Noise reducing brake pads

ABSTRACT

A brake pad for a motor vehicle is provided. The brake pad includes a body having upper and lower edges and a friction surface extending between the upper and lower edges for engaging a rotor. A notch is located along a section of the upper edge of the brake pad. The notch has an arc length of about ¼ to about ½ of an arc length of the pad and a depth of about ⅛ to about ⅙ of a height of the pad. During engagement with the rotor, the notch is configured to reduce squeal noise caused by tangential modes of the rotor.

TECHNICAL FIELD

The present disclosure relates generally to brake pads that reduce brakesqueal noise. More specifically, the present disclosure relates to brakepads that reduce brake squeal noise caused by brake rotor tangentialmodes.

BACKGROUND

Motor vehicle disc brake systems generally utilize a disc brake rotor ateach respective wheel (see FIG. 7). Each rotor, for example, generallyincludes two oppositely-facing annular friction surfaces which, duringoperation of the brakes, are engaged by two blocks of friction material(e.g., brake pads) that are moved towards one another into contact withthe two friction surfaces so that frictional forces occur and slow therotation of the rotor, and hence the wheel of the vehicle.

Accordingly, to slow and/or stop a vehicle, disc brake systems convertmost of the kinetic energy of the vehicle to thermal energy primarilythrough the frictional forces between the brake pads and the rotors ofthe vehicle. A small amount of this kinetic energy, however, may alsobecome vibrational energy within the brake system in both the brake pads(i.e., brake pad vibration) and rotors (i.e., rotor vibration). Thus,when damping of the brake system is low (which is often the case in theautomotive industry), such vibration can result in radiation of highfrequency sounds (e.g., over 1 kHz) from the brake system, otherwisereferred to as squeal noise. In other words, squeal noise may be createdby the dynamic instability of the brake system when the brake systemlinear vibration modes (i.e., pad and rotor vibrations) are placedclosely in their resonant frequency range, and there is sufficientenergy input to merge the modes, thereby creating an unstable complexsystem mode.

While this squeal noise does not indicate any functional imperfectionsor mechanical problems in the brake system, it may affect the driver'sperception of the vehicle's quality and the integrity of the brakesystem itself, which may lead, for example, to unnecessary warrantyclaims and costs. Accordingly, various countermeasures may be employedto address squeal noise problems, including, for example: 1) separatingthe brake system linear modes to prevent their merging, and/or 2)reducing the energy input from the rotor/pad interaction.

Traditional solutions for addressing brake squeal noise have, however,been generally focused on the separation between pad and rotor modes,where pad modes that align with rotor modes are modified to shift theirnatural frequencies away from the rotor mode frequencies. In otherwords, traditional solutions for addressing brake squeal noise havegenerally been focused on brake pad vibration (i.e., brake pad free-freevibration modes), without addressing rotor vibration (i.e., brake rotortension-compression natural vibration modes) or accounting for rotormode contribution such as rotor tangential modes.

It may, therefore, be advantageous to provide a brake pad design thatmay reduce energy input from the pad to the rotor that could otherwiseexcite rotor tangential modes, thus providing a brake pad design thataddresses and accounts for the rotor mode contribution to squeal noise.

SUMMARY

In accordance with various exemplary embodiments, a brake pad for amotor vehicle may include a body having upper and lower edges, afriction surface extending between the upper and lower edges forengaging a rotor, and a notch located along a section of the upper edge,wherein the notch has an arc length of about ¼ to about ½ of an arclength of the pad and a depth of about ⅛ to about ⅙ of a height of thepad, and wherein, during engagement with the rotor, the notch isconfigured to reduce squeal noise caused by tangential modes of therotor.

In accordance with various exemplary embodiments, a brake pad assemblyfor a motor vehicle may include a rigid backing structure, and afriction material carried by the rigid backing structure, the frictionmaterial having a notch located at a midpoint of an upper edge of thematerial, wherein the notch has an arc length of about ¼ to about ½ ofan arc length of the pad and a depth of about ⅛ to about ⅙ of a heightof the pad, and wherein, during braking of the motor vehicle, the notchis configured to reduce squeal noise caused by rotor tangential modes.

In accordance with various exemplary embodiments a method of reducingbrake squeal noise from rotor tangential modes may include removing aportion of a brake pad along a section of an upper edge of the pad, theportion being positioned and sized to prevent contact between a frictionsurface of the pad and a rotor, during engagement of the frictionsurface with the rotor, at an area of the rotor having a potential forhigh modal displacement in a tangential direction.

Additional objects and advantages of the disclosure will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the disclosure. Theobjects and advantages of the disclosure will be realized and attainedby means of the elements and combinations particularly pointed out inthe appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the disclosure, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure andtogether with the description, serve to explain the principles of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

At least some features and advantages will be apparent from thefollowing detailed description of embodiments consistent therewith,which description should be considered with reference to theaccompanying drawings, wherein:

FIG. 1 is a perspective view of a brake rotor illustrating out-of-planevibrations associated with a bending mode of the rotor;

FIG. 2 is a perspective view of a brake rotor illustratingtension-compression vibrations associated with a tangential mode of therotor;

FIGS. 3A-3C are schematic views of a brake rotor illustrating threedifferent tangential modes of the rotor;

FIG. 4 is a perspective view of the rotor of FIGS. 3A-3C illustratingthe tangential mode of FIG. 3B in greater detail;

FIG. 5 is a schematic view of a conventional brake pad positioned on arotor;

FIG. 6 is a schematic view of an exemplary brake pad in accordance withthe present disclosure positioned on a rotor;

FIG. 7 is a perspective view of an exemplary disk braking system inaccordance with the present disclosure;

FIG. 8 is an exploded view of the disk braking system of FIG. 7illustrating an exemplary embodiment of a brake pad assembly inaccordance with the present disclosure;

FIG. 9 is a graph illustrating brake noise associated with aconventional brake pad;

FIG. 10 is a graph illustrating brake noise associated with a brake padin accordance with the present disclosure having a 7 mm deep notch; and

FIG. 11 is a graph illustrating brake noise associated with a brake padin accordance with the present disclosure having a 10 mm deep notch.

Although the following detailed description makes reference toillustrative embodiments, many alternatives, modifications, andvariations thereof will be apparent to those skilled in the art.Accordingly, it is intended that the claimed subject matter be viewedbroadly.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. The variousexemplary embodiments are not intended to limit the disclosure. To thecontrary, the disclosure is intended to cover alternatives,modifications, and equivalents.

As above, during a braking event, the rotor and pads of a disk brakingsystem, such as, for example, a system 50 as illustrated in FIG. 7, mayexperience both normal and tangential forces at their interface. Forcesacting normal to the rotor and pad surfaces (i.e., normal forces) caninduce bending or out-of-plane vibrations in the rotor and pad, whichcan be associated with rotor bending modes as illustrated, for example,in FIG. 1. Forces acting tangentially on the surfaces of the rotor(i.e., tangential forces) also may develop tension-compressionvibrations within the rotor, which can be associated with rotortangential modes (otherwise referred to as in-plane or circumferentialmodes) as illustrated, for example, in FIG. 2. These modes result inradiation of high frequency sounds from the brake system, otherwisereferred to as squeal noise.

In the audible frequency range (i.e., about 20 Hz to about 20 kHz) atypical disk brake rotor 1 (see FIGS. 3 and 4) has up to 20 pairs (sinand cosine) of the bending modes and 3 pairs (sin and cosine) of thetangential modes at distinct resonant frequencies. The three rotortangential modes are illustrated, for example, in FIGS. 3A-3C. As above,while both bending and tangential rotor modes can be responsible forbrake squeal noise generation, the bending modes contribution to squealnoise is already well studied and understood, resulting in a variety ofeffective countermeasures available when needed. For example, the lengthof lining material on the brake pads may be shortened to avoid modalalignment between the pad and rotor bending modes, which can promote thecreation of system unstable modes. At the same time, however, thegeneration of squeal noises due to the rotor tangential modes often isnot addressed. Various embodiments of the present disclosure, therefore,contemplate providing effective countermeasures against squeal noisesproduced by rotor tangential modes.

In accordance with various embodiments, for example, the presentdisclosure contemplates a brake pad design that may reduce the energyinput from the surface contact between the pad and rotor surfaces, whichwould otherwise excite rotor tangential modes, thereby eliminating anypotential for brake squeal noise caused by such modes. FIG. 4, forexample, is a perspective view of the rotor 1 of FIGS. 3A-3Cillustrating the tangential mode of FIG. 3B in greater detail. As shownin FIG. 4, in the rotor tangential mode, points P on a diametric line Dmove in phase in the tangential (or circumferential) direction, whereinthe absolute vibration amplitude increases along with the distance fromthe rotor axis A and has its maximum value at the outer diameter of therotor 1. Thus, the easiest way to excite the rotor tangential mode is toexcite the rotor at the outer diameter of the rotor in itscircumferential direction.

As illustrated in FIG. 5, when engaged with the rotor 1 (i.e., during abraking event), a conventional brake pad 10 generally covers the outerdiameter of the rotor within an arc length L_(arc) of the pad 10.Therefore, the pad 10 has a tendency to excite the rotor tangentialmodes via the surface contact between the pad 10 and the rotor 1 at theouter diameter of the rotor 1. Various embodiments of the presentdisclosure, therefore, propose a unique brake pad design that minimizesthe surface contact between the pad and rotor at the outer diameter ofthe rotor 1.

In accordance with various embodiments, for example, the presentdisclosure contemplates brake pads having a notch located along asection of an upper edge of the pad to reduce the surface contactbetween the pad and rotor at the outer diameter of the rotor. In otherwords, each of the exemplary brake pads described herein has a notchthat is positioned along the arc length L_(arc) of the pad, wherein thearc length L_(arc) is configured to align with the outer diameter of therotor when the pad is engaged with the rotor. The pad, therefore, doesnot cover the entire outer diameter of the rotor (i.e., with its arclength L_(arc)), which functions to shift down the effective radius ofthe surface contact area (i.e., between the pad and rotor), therebyreducing the energy input from the rotor/pad interaction to preventexcitation of the rotor tangential modes.

As described above, as used herein the terms “rotor tangential modes” or“tangential modes of the rotor” refer to the forces acting tangentiallyon the surfaces of a brake rotor (i.e., tangential forces), whichdevelop tension-compression vibrations within the rotor as illustrated,for example, in FIG. 2. These modes are known to result in radiation ofhigh frequency sounds from the brake system, otherwise referred to assqueal noise.

FIG. 6 illustrates an exemplary embodiment of a brake pad 100 inaccordance with the present disclosure. The brake pad 100 includes abody 102 having an upper edge 103, a lower edge 104, and a frictionsurface 105 extending between the upper and lower edges 103, 104. Asabove, when positioned within a braking system (see FIGS. 7 and 8) of avehicle (not shown), the friction surface 106 is configured to engage arotor, such as, for example, the rotor 1 to stop and/or slow thevehicle.

In various embodiments, for example, brake pads in accordance with thepresent disclosure may comprise an assembly including a rigid backingstructure and a friction material that is carried by the rigid backingstructure. As illustrated in FIGS. 7 and 8, a brake pad assembly 200 mayinclude a rigid backing structure 201, such as, for example, a metallicbacking plate, and a friction material 202 that is carried by the rigidbacking structure 201. The friction material 202 is made, for example,from a material and/or combination of materials which have a highcoefficient of friction and which may also absorb and disperse largeamounts of heat. In various embodiments, for example, the frictionmaterial 202 may include a non-asbestos organic, semi-metallic, and/orceramic material.

Those of ordinary skill in the art would understand, however, that brakepad assemblies in accordance with the present disclosure may includevarious types and/or configurations of backing structures and frictionmaterials, which are formed from various materials, based on aparticular braking application. Furthermore, brake pad assemblies inaccordance with the present disclosure may include additional componentsand/or materials, including, for example, a shim (not shown) attached toan outer surface of the backing structure to help correct smalldifferences (which may sometimes also lead to noise) between the backingstructure and a caliper to which it is attached.

As perhaps best shown in FIG. 8, in various exemplary embodiments, thefriction material 202 is bound to a surface of the backing plate 201 tocreate a friction surface 205 that is configured to face the brake rotor1 when positioned within the motor vehicle (not shown), and an oppositesurface of the backing plate 201 is configured to be attached to acaliper 70 when positioned within the vehicle. In various embodiments,for example, two brake pads (i.e., assemblies 200) may be containedwithin the brake caliper 70 (i.e., positioned over a cheek portion ofthe rotor 1) with their friction surfaces 205 facing the rotor 1. Inthis manner, when the brakes are applied, the caliper 70 clamps orsqueezes the two pads 200 together onto the spinning rotor 1 to slowand/or stop the vehicle.

With reference again to FIG. 6, the body 102 of the pad 100 furtherincludes a notch 106 that is located along a section of the upper edge103 of the pad 100, such as, for example, a center section of the upperedge 103 as shown in FIG. 6. And, as above, the notch 106 is configuredto reduce squeal noise caused by tangential modes of the rotor 1 duringengagement of the pad 100 with the rotor 1. In other words, the notch106 is positioned and sized, such that during engagement with the rotor1, there is minimal contact between the friction surface 105 of the pad100 and the rotor 1 at or near an outer diameter D_(out) of the rotor 1in a circumferential direction C. As above, for example, with referenceto FIG. 4, the absolute vibration amplitude of the rotor 1 increasesalong with the distance from the rotor axis A with a maximum value atthe outer diameter D_(out) of the rotor 1. Accordingly, depending on theresonant frequency that may be created in the rotor 1, and thecorresponding tangential mode related to that frequency (see FIGS.3A-3C), various areas along the outer diameter D_(out) of the rotor 1may have potential for high modal displacement in a tangential directionof the rotor 1. Thus, in various embodiments, the notch 106 may bepositioned and sized such that, during engagement with the rotor 1, thebrake pad 100 does not cover the entire outer diameter D_(out) of therotor (i.e., with its arc length L_(arc)), such that there is relativelyno contact between the friction surface 105 and the rotor 1 at an areaof the rotor 1 having a potential for high modal displacement in atangential direction.

In various embodiments, for example, the notch 106 is u-shaped, with anarc length L_(arc-notch) and a depth d, and is centered along a midpointof an arc length L_(arc) of the brake pad 100. In this manner, when thebrake pad 100 is engaged with the rotor 1, the brake pad will not coverthe entire outer diameter D_(out) of the rotor 1 along its arc lengthL_(arc), thereby shifting down the effective radius of the contact areabetween the friction surface 105 and the rotor 1. Although, to maximizesqueal noise reduction, it may be considered optimal to shift down theeffective radius of the contact area across the total arc length L_(arc)of the pad 100 (and not just along a portion of the arc length L_(arc)),it may not always be feasible to do so. For example, when in use, asurface corrosion layer may develop at the rotor surface not swept bythe pad 100, which may impact the overall appearance of the brake rotor1 and affect customer perception of the quality of the vehicle.

Accordingly, in accordance with various embodiments, the arch lengthL_(arc-notch) of the notch 106 does not exceed about 50% of the totalarc length L_(arc) of the pad 100. It is generally considered that sucha configuration will ensure that there is enough remaining liningmaterial to clean up surface corrosion layers that could develop when,for example, the vehicle is parked in humid conditions. Thus, in variousexemplary embodiments, the arch length L_(arc-notch) of the notch 106 isabout ¼ to about ½ the arc length L_(arc) of the pad 100, and the depthd of the notch 106 is about ⅛ to about ⅙ of a height H of the pad 100.In other words, for brake pads most commonly used in the automotiveindustry, the arch length L_(arc-notch) of the notch 106 is about 40 mmto about 80 mm, and the depth d of the notch 106 is about 8 mm to about12 mm.

The present disclosure, however, contemplates pads having any number,configuration (i.e., dimension and/or geometry), and/or shape of notches106 based on a particular application. Those of ordinary skill in theart would understand, therefore, that the brake pad 100 illustrated inFIG. 6 is exemplary only and intended to illustrate one embodiment ofthe present disclosure. Accordingly, brake pads in accordance with thepresent disclosure may also have various dimensions, shapes, and/orconfigurations, without departing from the scope of the presentdisclosure and claims. Moreover, to further reduce brake squeal noise,brake pads in accordance with the present disclosure may also utilizeother known methods and techniques in combination with the disclosednotch design. As illustrated in FIG. 8, various additional embodimentscontemplate, for example, employing slots 208 and additional notches 210in combination with a notch 206 (the disclosed notch design) in order toalso address squeal noise caused, for example, by rotor bending modes(i.e., to address noise issues not caused by rotor tangential modes).

A disk brake system utilizing a brake pad design in accordance with thepresent disclosure, similar to the brake pad 100 illustrated anddescribed above with reference to FIG. 6, was modeled in Adams, aMultibody Dynamics (MBD) simulation software by MSC Software®. A diskbrake system utilizing a conventional brake pad design similar to thebrake pad 10 illustrated in FIG. 5 was also modeled in Adams forcomparison purposes. To verify the expected noise reduction capabilitiesof the brake pads and assemblies in accordance with the presentdisclosure, brake system testing was conducted on a brake NVHdynamometer using SAE J2521 test procedure. The test results are shownin FIGS. 9-11.

FIGS. 9-11 are graphs respectively illustrating the rotor tangentialmode at a frequency of 9.8 kHz for the conventional brake pad (with nonotch), a brake pad having a 7 mm deep u-shaped notch, and a brake padhaving a 10 mm deep u-shaped notch. As illustrated in FIG. 9, the squealnoise produced by the modeled conventional brake pad (via the rotortangential mode) far exceeded the target established noise level. Inother words, the conventional pad produced a maximum noise of about 88decibels, which exceeded the target level (which would be consideredacceptable to a driver of the vehicle) of 70 decibels as measured at thewheel end.

As illustrated in FIG. 10, although the squeal noise produced by themodeled brake pad with a 7 mm notch (via the rotor tangential mode)still exceeded the target established noise level in two instances, theoccurrences of squeal noises exceeding the target was greatly reduced.

Finally, as illustrated in FIG. 11, the squeal noise produced by themodeled brake pad with a 10 mm notch (via the rotor tangential mode) waswell below the target established noise level. In other words, the brakepad with the 10 mm notch produced a maximum noise of about 54 decibels,which was well below the target level of 70 decibels.

It was, therefore, determined that the disclosed brake pad design cansignificantly reduce brake squeal noise associated with rotor tangentialmodes, and that when utilizing notches having depths greater than about8 mm, such noises may be completely reduced to an acceptable level.

The present disclosure further contemplates methods of reducing brakesqueal noise from rotor tangential modes, such as, for example, by usingthe brake pads 100 described above with reference to FIG. 6. Inaccordance with various exemplary embodiments, to reduce brake squealnoise from rotor tangential modes, a portion of the brake pad 100 may beremoved along a section of an upper edge 103 of the pad 100. As above,in accordance with various embodiments, the removed portion may bepositioned and sized to prevent contact between a friction surface 105of the pad 100 and a rotor 1, during engagement of the friction surface105 with the rotor 1, at an area of the rotor 1 having a potential forhigh modal displacement in a tangential direction.

As above, with reference to FIG. 4, the absolute vibration amplitude ofthe rotor 1 increases along with the distance from the rotor axis A,with a maximum value at the outer diameter D_(out) of the rotor 1.Accordingly, depending on the resonant frequency that may be created inthe rotor 1, and the corresponding tangential mode related to thatfrequency (see FIGS. 3A-3C), various areas along the outer diameterD_(out) of the rotor 1 may have potential for high modal displacement ina tangential direction of the rotor 1. Thus, as above, the removedportion may be positioned and sized such that, during engagement withthe rotor 1, the brake pad 100 does not cover the entire outer diameterD_(out) of the rotor (i.e., with its arc length L_(arc)), such thatthere is relatively no contact between the friction surface 105 and therotor 1 at such areas. In other words, the removed portion may bepositioned and sized to minimize contact between the friction surface105 of the pad 100 and the rotor 1 at or near the outer diameter D_(out)of the rotor 1 in a circumferential direction.

In various embodiments, for example, the removed portion may include au-shaped portion, such as, for example, a u-shaped notch 106 that islocated along a center section of the upper edge 103 of the pad 100. Thenotch 106 may have an arc length L_(arc-notch) and a depth d, and becentered along a midpoint of an arc length L_(arc) of the brake pad 100.In this manner, when the brake pad 100 is engaged with the rotor 1, thebrake pad will not cover the entire outer diameter D_(out) of the rotor1 along its arc length L_(arc), thereby shifting down the effectiveradius of the contact area between the friction surface 105 and therotor 1. In various embodiments, for example, the arch lengthL_(arc-notch) of the notch 106 is about ¼ to about ½ the arc lengthL_(arc) of the pad 100, and the depth d of the notch 106 is about ⅛ toabout ⅙ of a height H of the pad 100. In other words, for brake padsmost commonly used in the automotive industry, the arch lengthL_(arc-notch) of the notch 106 is about 40 mm to about 80 mm, and thedepth d of the notch 106 is about 8 mm to about 12 mm.

As above, however, the present disclosure contemplates pads having anynumber, configuration (i.e., dimension and/or geometry), and/or shape ofnotches 106 based on a particular application.

While the present disclosure has been disclosed in terms of exemplaryembodiments in order to facilitate better understanding of thedisclosure, it should be appreciated that the disclosure can be embodiedin various ways without departing from the principle of the disclosure.Therefore, the disclosure should be understood to include all possibleembodiments which can be embodied without departing from the principleof the disclosure set out in the appended claims. Furthermore, althoughthe present disclosure has been discussed with relation to automotivevehicles, those of ordinary skill in the art would understand that thepresent teachings as disclosed would work equally well for any type ofvehicle having a braking system that utilizes pads and rotors.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the written description and claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the present disclosure. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” include plural referents unlessexpressly and unequivocally limited to one referent. Thus, for example,reference to “a sensor” includes two or more different sensors. As usedherein, the term “include” and its grammatical variants are intended tobe non-limiting, such that recitation of items in a list is not to theexclusion of other like items that can be substituted or added to thelisted items.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the system and method of thepresent disclosure without departing from the scope its teachings. Otherembodiments of the disclosure will be apparent to those skilled in theart from consideration of the specification and practice of theteachings disclosed herein. It is intended that the specification andembodiment described herein be considered as exemplary only.

1. A brake pad comprising: a body having upper and lower edges, afriction surface extending between the upper and lower edges forengaging a rotor, and a notch located along a section of the upper edge,wherein the notch has an arc length of about ¼ to about ½ of an arclength of the brake pad and a depth of about ⅛ to about ⅙ of a height ofthe brake pad, and wherein, during engagement with the rotor, the notchis configured to reduce squeal noise caused by tangential modes of therotor.
 2. The brake pad of claim 1, wherein the notch is u-shaped. 3.The brake pad of claim 1, wherein the notch is centered along a midpointof the arc length of the pad.
 4. The brake pad of claim 1, wherein thearc length of the notch is about 40 mm to about 80 mm.
 5. The brake padof claim 1, wherein the depth of the notch is about 8 mm to about 12 mm.6. The brake pad of claim 1, wherein the tangential modes includetension-compression natural vibration modes of the rotor.
 7. The brakepad of claim 1, wherein the notch is positioned such that, duringengagement with the rotor, there is minimal contact between the frictionsurface and the rotor at or near an outer diameter of the rotor in acircumferential direction.
 8. The brake pad of claim 1, wherein thenotch is positioned such that, during engagement with the rotor, thereis relatively no contact between the friction surface and the rotor atan area of the rotor having a potential for high modal displacement in atangential direction.
 9. A brake pad assembly for a motor vehicle,comprising: a rigid backing structure; and a friction material carriedby the rigid backing structure, the friction material having a notchlocated at a midpoint of an upper edge of the material, wherein thenotch has an arc length of about ¼ to about ½ of an arc length of thebrake pad and a depth of about ⅛ to about ⅙ of a height of the brakepad, and wherein, during braking of the motor vehicle, the notch isconfigured to reduce squeal noise caused by rotor tangential modes. 10.The brake pad assembly of claim 9, wherein the notch is u-shaped. 11.The brake pad assembly of claim 9, wherein the arc length of the notchis about 40 mm to about 80 mm.
 12. The brake pad assembly of claim 9,wherein the depth of the notch is about 8 mm to about 12 mm.
 13. Thebrake pad assembly of claim 9, wherein the tangential modes includetension-compression natural vibration modes.
 14. The brake pad of claim9, wherein the notch is positioned such that, during braking of themotor vehicle, there is minimal contact between the friction materialand a rotor of the motor vehicle at or near an outer diameter of therotor in a circumferential direction.
 15. The brake pad of claim 9,wherein the notch is positioned such that, during braking of the motorvehicle, there is relatively no contact between the friction surface anda rotor of the motor vehicle at an area of the rotor having a potentialfor high modal displacement in a tangential direction.
 16. A method ofreducing brake squeal noise from rotor tangential modes, comprising:removing a portion of a brake pad along a section of an upper edge ofthe pad, the portion being positioned and sized to prevent contactbetween a friction surface of the pad and a rotor, during engagement ofthe friction surface with the rotor, at an area of the rotor having apotential for high modal displacement in a tangential direction.
 17. Themethod of claim 16, wherein removing the portion comprises removing au-shaped portion of the pad along a center section of the upper edge ofthe pad.
 18. The method of claim 17, wherein removing the u-shapedportion comprises removing a notch having an arc length of about ¼ toabout ½ of an arc length of the pad and a depth of about ⅛ to about ⅙ ofa height of the pad.
 19. The method of claim 18, wherein the arc lengthof the notch is about 40 mm to about 80 mm and the depth of the notch isabout 8 mm to about 12 mm.
 20. The method of claim 16, wherein theportion is positioned and sized to minimize contact between the frictionsurface of the pad and the rotor at or near an outer diameter of therotor in a circumferential direction.